This application claims, under 35 USC 119, priority of Japanese Application No. 2000-381444 filed Dec. 15, 2000.
1. Field of the Invention
The present invention relates to a motor, and more particularly to a motor which is accommodated within a rotary cylindrical core of, for example, a shutter opening/closing apparatus and used to rotate the rotary cylindrical core.
2. Description of the Related Art
Conventionally, in many cases, as shown in FIG. 17, a stator core of a motor is formed of a plurality of square substrates 012 made of magnetic material and arranged in layers, each of the square substrates 012 being punched at a central portion thereof such that projections 014 which are to become NS poles project radially inward. The plurality of substrates 012 are integrated into a stator core through pole caulking, riveting, or bonding. Field coils are formed on NS poles of the thus-formed stator core, thereby yielding a stator. In FIG. 17, reference numeral 040 denotes holes through which corresponding rivets are inserted.
Being sandwiched by right and left brackets, which support right and left ends of a rotor shaft by means of bearings, the stator is clamped therebetween by means of bolts which extend axially through the right and left brackets and the stator. The right and left brackets not only support the right and left ends of the rotor shaft but also clamp the stator from right and left sides, thereby yielding a main portion of a motor.
The thus-assembled motor assumes the profile of a square prism, since the stator core assumes the profile of a square prism. The reason why the profile of a square prism is employed is that it is necessary to pass the aforementioned bolts through four corners of the square prism, to thereby clamp, through tightening of the bolts, the stator sandwiched between the right and left brackets. In FIG. 17, through holes 041 are formed at four corners of the substrate 012 in order to enable passage of such bolts therethrough.
Notably, the stator core may assume a cylindrical profile through use of circular substrates, whereas the right and left brackets assume the profile of a square prism. In this case, the bolts extend through merely the right and left brackets at four corners while the cylindrical stator is sandwiched between the right and left brackets. The bolts are tightened to thereby clamp the stator between the right and left brackets. However, in either case, at least a portion of the motor has the profile of a square prism.
When the thus-assembled motor assuming partially or entirely the profile of a square prism is applied to, for example, a shutter opening/closing apparatus, the motor is accommodated within a rotary cylindrical core for releasing/taking up a shutter and is fixedly supported by a shutter frame surrounding the shutter, independently of the rotary cylindrical core. By virtue of this structure, the rotary cylindrical core can be rotated through drive of the motor. In this case, since the motor having the profile of a square prism is placed within the rotary cylindrical core, a useless space is formed within the rotary cylindrical core, resulting in an increase in size of the rotary cylindrical core.
A conceivable measure to solve the above problem is to eliminate the portion having the profile of a square prism from the motor such that the entire motor profile assumes a cylindrical form. As a result, an idle space can be eliminated from inside the rotary cylindrical core. However, even in this case, the bolts used to clamp the center stator between the right and left brackets must extend through the right and left brackets and the stator in a radially outward extension region where the bolts do not disturb magnetic flux extending through the stator core. In order to establish such extension region, the diameter of the motor is unavoidably increased, with a resultant increase in the size of the rotary cylindrical core. This problem is unavoidable as long as a previously assembled motor is to be incorporated into the rotary cylindrical core.
In order to cope with the problem, instead of a previously assembled motor being incorporated into the rotary cylindrical core, there has been employed a method of assembling within the rotary cylindrical core a motor whose diameter corresponds to the inner diameter of the rotary cylindrical core. Specifically, a stator, brackets, a rotor, and other motor components are sequentially incorporated into the rotary cylindrical core, followed by final axial clamping of the components.
Even the above method involves the following problem. The motor must be tested for characteristics while being incorporated within the rotary cylindrical core. When the test reveals that the motor involves a characteristic problem, the motor must be removed from the rotary cylindrical core. Since the removed motor is in the form of discrete components, the motor cannot be tested for characteristics outside the rotary cylindrical core.
An object of the present invention is to solve the above-mentioned problems in the conventional motor and to provide a motor in which a stator can be clamped between right and left brackets to thereby be fixed to these brackets, without an unnecessary increase in the diameter thereof, even when a portion having the profile of a square prism is removed from the motor such that the entire motor profile assumes a cylindrical form.
Another object of the present invention is to provide a motor which has a compact, robust, simple, and easy-to-assemble structure.
Still another object of the present invention is to provide a motor which can be incorporated into a rotary cylindrical core of, for example, a shutter opening/closing apparatus after the motor is assembled and tested for characteristics outside the rotary cylindrical core, without involvement of increase in the inside diameter of the rotary cylindrical core.
To achieve the above object, the present invention provides a motor comprising a rotor having a rotor shaft, a stator having a stator core, right and left brackets, and a plurality of binders. The stator core comprises a plurality of circular substrates arranged in layers. The stator core has a plurality of first grooves formed on the cylindrical outer surface thereof such that the first grooves are arranged at predetermined spacing along a circumferential direction and extend in an axial direction. The right and left brackets each assume the form of a bottomed cylinder. The right and left brackets each comprise a bearing portion formed at a bottom portion in order to support the rotor shaft. A plurality of engagement projections are formed at an axially inner end of each of the right and left brackets in such a manner as to project axially inward so as to be fitted into the first grooves. A plurality of second grooves are formed on cylindrical outer surface of each of the right and left brackets such that the second grooves are arranged at predetermined spacing along the circumferential direction and extend in the axial direction and such that the second grooves formed on the right bracket are aligned with those formed on the left bracket. The binders each have opposite ends bent so as to form engagement portions and are fitted into the second grooves such that the engagement portions thereof are engaged with axially outer ends of the right and left brackets to thereby clamp the stator core axially inward from opposite sides.
Through employment of the above structure, the right and left brackets can be clamped while being urged toward each other, to thereby firmly clamp the stator therebetween.
Without use of clamp bolts as practiced conventionally; i.e., merely through the binders being fitted onto the right and left brackets, the right and left brackets can be clamped while being urged toward each other, to thereby firmly clamp the stator therebetween. Thus, motor assembly work and motor structure can be simplified.
Since clamp bolts, employment of which leads to increase in motor diameter, are not employed, it is possible to eliminate the radially outward extension region which has conventionally been provided in order to enable passage of clamp bolts through the right and left brackets and the stator and which has a radius that does not disturb magnetic flux extending through the stator core. Therefore, it becomes possible to reduce the size of the motor, while making the motor have a cylindrical profile. Thus, in application as a drive unit to, for example, a rotary cylindrical core of a shutter opening/closing apparatus, the motor of the present invention can be incorporated into the rotary cylindrical core after the motor is assembled and tested for characteristics outside the rotary cylindrical core, without involvement of increase in the inside diameter of the rotary cylindrical core. Thus, such apparatus to which the motor is applied can be reduced in size, and the motor can be readily tested for characteristics.
Furthermore, through engagement of the first grooves formed in the stator with the engagement projections of the right and left brackets, the stator can be positioned along the circumferential direction, the radial direction, and the axial direction, thereby enabling robust assembly of the motor.
Preferably, the first grooves are dovetail grooves. Through engagement with the first grooves; i.e., dovetail grooves formed on the stator, the engagement projections of the right and left brackets never come off the dovetail grooves along the circumferential direction and the radial direction. Thus, the stator can be positioned reliably along the circumferential direction, the radial direction, and the axial direction, thereby enabling robust assembly of the motor in a more reliable manner.
Preferably, the second grooves are shallow grooves whose cross sections each assume the shape of a squarish letter U. Thus, the second grooves to be engaged with the binders can be formed on the cylindrical outer surfaces of the right and left brackets without the surfaces being machined to a great extent, thereby having no adverse effect on the structural strength of the right and left brackets.
Preferably, the engagement portions of the binders each comprise a protrusion projecting axially inward, and a plurality of recesses are formed on axially outer end surfaces of the right and left brackets, so as to be engaged with the protrusions. Since the opposite ends of the binders are reliably engaged with the axially outer ends of the right and left brackets, the binders are reliably fitted onto the right and left brackets. Thus, the binders clamp the right and left brackets in such a manner as to urge the brackets toward each other, to thereby firmly clamp the stator therebetween. Therefore, the motor can be assembled more robustly.
The present invention further provides a motor comprising a rotor having a rotor shaft, a stator having a stator core, and right and left brackets. The stator core comprises a plurality of circular substrates arranged in layers. The stator core has a plurality of dovetail grooves formed on the cylindrical outer surface thereof such that the dovetail grooves are arranged at predetermined spacing along the circumferential direction and extend in the axial direction. The right and left brackets each assume the form of a bottomed cylinder. The right and left brackets each comprise a bearing portion formed at a bottom portion so as to support the rotor shaft. A plurality of engagement projections are formed at an axially inner end of each of the right and left brackets in such a manner as to project axially inward so as to be fitted into the dovetail grooves. Opening edge portions of the dovetail grooves are caulked while the engagement projections are fitted into the dovetail grooves, so as to fix the engagement projections and the dovetail grooves to each other, to thereby clamp the stator core axially inward from opposite sides.
Through employment of the above structure, the right and left brackets can be clamped while being urged toward each other, to thereby firmly clamp the stator therebetween.
Without use of clamp bolts as practiced conventionally; i.e., merely through opening edge portions of the dovetail grooves being caulked, the right and left brackets can be clamped while being urged toward each other, to thereby firmly clamp the stator therebetween. Thus, motor assembly work and motor structure can be simplified.
Since clamp bolts, employment of which leads to increase in motor diameter, are not employed, it is possible to eliminate the radially outward extension region which has conventionally been provided in order to enable passage of clamp bolts through the right and left brackets and the stator and which has a radius that does not disturb magnetic flux extending through the stator core. Therefore, it becomes possible to reduce the size of the motor, while making the motor have a cylindrical profile. Thus, in application as a drive unit to, for example, a rotary cylindrical core of a shutter opening/closing apparatus, the motor of the present invention can be incorporated into the rotary cylindrical core after the motor is assembled and tested for characteristics outside the rotary cylindrical core, without involvement of increase in the inside diameter of the rotary cylindrical core. Thus, such apparatus to which the motor is applied can be reduced in size, and the motor can be readily tested for characteristics.
Furthermore, through engagement of the first grooves formed in the stator with the engagement projections of the right and left brackets, the stator can be positioned along the circumferential direction, the radial direction, and the axial direction, thereby enabling robust assembly of the motor.